Single-wall carbon nanotubes (SWCNTs) are one of the most extensively produced carbon materials and the environmental, public and professional exposure is therefore dramatically increasing. Consequently the studies on bio-effects and safety of SWCNTs are highly needed. The goal of this study was investigate the effects in vitro of SWCNTs in cells of the oral cavity, never employed in this research field. We exposed human gingival fibroblasts to 50, 75, 100, 125, 150μg/ml SWCNTs for 24h and we investigated genotoxicity (Comet assay and micronucleus test), cytotoxicity, oxidative stress, as reactive oxygen species (ROS) generation, and stress response, as Heat shock protein 70 (Hsp70) expression. SWCNTs produced genotoxic effects at all doses, even if detected with different sensitiveness by the two tests, and at the two highest doses induced a strong decrease of the cell proliferation and cell survival, causing apoptosis too. Furthermore, we proved the ability of these nanomaterials to induce oxidative stress and Hsp70 expression. Finally, by inhibition of Hsp70 expression, we demonstrated that this heat shock protein conferred protection against SWCNT geno-cytotoxicity.